Chiral Phosphoric Acid Directed Regioselective Acetalization of Carbohydrate-Derived 1,2-Diols

摘要

A number of important classes of natural products such as oligosaccharides or polyketides are polyols, and synthetic approaches to the regioselective functionalization of such compounds almost invariably involve multiple protecting group manipulations. In contrast, nature utilizes a more direct approach and relies on enzymes to achieve selective functionalization of less reactive sites within a complex molecule. Recent findings suggest that small-molecule-based chiral catalysts could act similarly to enzymes and enhance or alter the inherent selectivity profiles exhibited by the substrates. While there is a wide range of electrophiles that could be activated through Lewis base catalysis, no catalysts allowing regioselective trapping of oxocarbenium ions (or their equivalent) have been reported to date.